Add tests directory and GitHub Actions workflow for CI

.github/workflows/test.yml

@@ -0,0 +1,37 @@
+name: Test-QCD-Pipeline
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Set up Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.10'  
+
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install pytest snakemake  
+
+      - name: Install Singularity
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y singularity-container
+
+      - name: Run Snakemake tests
+        run: |
+          pytest test_pipeline.py  
+